1. Field of Invention
The present invention relates to an apparatus for driving a panel in a display system. More particularly, the present invention relates to an apparatus for driving a panel in a thin-film-transistor liquid crystal display (TFT-LCD) system.
2. Description of Related Art
In a TFT-LCD system, there is usually a reset device detecting a supply voltage for the LCD system and asserting a control signal, i.e. XAO signal, transmitted to a gate driver of the LCD system. When the LCD system is powered off, the supply voltage decreases, and the reset device asserts the XAO signal, such that the outputs of the gate driver are all at a high level, and all rows of pixels on the panel are thus turned on to be discharged.
FIG. 1 shows a gate driver receiving the control signal. The gate driver 100 has an input terminal 106 for receiving the control signal, i.e. XAO signal, and includes a resistor 102 and an electrostatic discharge (ESD) protection device 104. One end of the resistor 102 is coupled to the supply voltage VDD, and the other end of the resistor 102 is coupled electrically to the input terminal 106. The ESD protection device 104 is coupled between the input terminal 106 and the resistor 102.
During a normal operation of the LCD system, the resistor 102 keeps the XAO signal at a high level. When the LCD system is powered off, the supply voltage VDD decreases, and the reset device (not shown) asserts the XAO signal by an open-drain MOSFET (not shown). However, when the supply voltage VDD continues to decrease, the turn-on resistance of the open-drain MOSFET increases gradually, so that the XAO signal cannot be kept at a low level indeed; that is, the XAO signal would be affected by the resistor 102 to increases gradually. Therefore, the outputs of the gate driver cannot be kept at a high level to turn on the pixels on the panel.